Hillary Clinton left the 9/11 memorial early on Sunday. Her campaign said she felt overheated.

Democratic nominee Hillary Clinton abruptly left a memorial event in New York City on Sunday morning. The Clinton campaign later said that she felt overheated and went to recuperate at her daughter’s apartment.

“Secretary Clinton attended the September 11th Commemoration Ceremony for just an hour and thirty minutes this morning to pay her respects and greet some of the families of the fallen,” a statement from the campaign read. “During the ceremony, she felt overheated so departed to go to her daughter’s apartment, and is feeling much better.”

The incident took place at a crowded ceremony in downtown Manhattan, with temperatures in the high 70s and low 80s. According to reports, Clinton departed from the memorial without her accompanying press corps. The campaign initially declined to tell reporters where she was headed and speculation ensued that she had been whisked away in a health-related episode. Details of what actually transpired are scant.

But in a video of the incident, Clinton appears to buckle at the knees as she moves from the curb into her car, requiring the help of aides and what appears to be an agent to get into the vehicle. Hours later, additional video showed her looking refreshed as she left her daughter Chelsea’s apartment.

“I’m feeling great,” she said, waving to the cameras. “It’s a beautiful day in New York.” She later headed to her home in Chappaqua, New York.

On Sunday afternoon, the campaign released a statement from Clinton’s doctor, Dr. Lisa Bardack, who said Clinton had pneumonia and was suffering on Sunday from being overheated. The full statement is below:

“Secretary Clinton has been experiencing a cough related to allergies. On Friday, during follow up evaluation of her prolonged cough, she was diagnosed with pneumonia. She was put on antibiotics, and advised to rest and modify her schedule. While at this morning’s event, she became overheated and dehydrated. I have just examined her and she is now re-hydrated and recovering nicely.”

Responding to a Washington Post report that speculated that the Secret Service followed “atypical protocol” in handling Clinton’s early departure, the Secret Service issued a statement stressing that “at no time did [it] violate security protocols” and said it was “confident in the actions taken by its Protective Detail earlier today.”

FACT CHECK: At no time did @SecretService personnel violate security protocols during the early departure of one of our protectees.

The episode will likely spark further attempts by Republicans to question Clinton’s fitness for office. GOP nominee Donald Trump has repeatedly insinuated that Clinton is in poor health, a storyline that conservative outlets like the Drudge Report and Fox News’ Sean Hannity have pushed.

There has been little evidence to support these claims. Clinton suffered a concussion in 2012 from a fall that her doctor said was due to dehydration. As Clinton, 68, launched her presidential campaign in 2015, her longtime physician, Dr. Lisa Bardack, released a statement on her health, writing:

Mrs. Clinton is a healthy female with hypothyroidism and seasonal allergies, on long-term anticoagulation. She participates in a healthy lifestyle and has had a full medical evaluation, which reveals no evidence of additional medical issues or cardiovascular disease. Her cancer screening evaluations are all negative. She is in excellent physical condition and fit to serve as President of the United States.

Trump, who at 70 is two years older than Clinton, also released a letter from a doctor late last year, which stated that the businessman’s health was “extraordinarily excellent.” The physician, Dr. Harold Bornstein, later said he wrote the letter in just five minutes, while a Trump limousine waited outside his office.

The GOP nominee is set to appear on Dr. Oz’s television show this week to discuss his “personal health regimen.”

This article has been updated to include statements from Dr. Lisa Bardack and the Secret Service and reports that campaign officials have canceled Clinton’s travel plans for Monday.